A Warning connection status with the message One or more engines are not working happens in a multi-engine environment when the connection fails in one of the engines. Other engines may be working correctly on the same connection, or have not tried to open the connection yet.
Check the engine logs on the computers where the engines are installed to find out which one is failing.
Perform connection troubleshooting on the failing engine. Be sure that QlikView documents and network shares are accessible or QlikView Server are reachable from that particular computer.